1. Field of the Invention
The invention is directed to printing on edibles with ink-jet compatible ink. In particular, the invention is directed to modifying the surface characteristics of edibles to facilitate printing with water-based inks which are typically used in inkjet printing. The invention has particular applicability to methods of printing high-resolution images on soft panned and hard panned sugar shell confectionery.
2. Description of the Related Art
It is known to print identifying or decorative images on edibles, including hard panned sugar shell confectionery, such as M&M's® brand peanut and chocolate candies. Ink-jet printing eliminates the need to contact the edible substrate with a contact member such as a pad or roller. Since ink-jet printing is a non-contact printing system, slight variations in the size of edibles do not negatively impact upon printing quality, as typically occurs with pad or roller based systems. Also, an ink-jet printer image is stored as data, and not fixed on the contact member. Consequently, the overall speed and throughput of printing on edibles is increased if an ink-jet printer is used, and images can be selected, altered, transmitted, and the like, more easily than in pad printing or offset printing.
A method of ink-jet printing on edibles is described in co-pending U.S. patent application Ser. No. 09/557,108, incorporated herein by reference. A method for printing multicolor images on the surfaces of shaped edible pieces is described in co-pending U.S. patent application Ser. No. 09/479,549, also incorporated herein by reference.
Ink-jet printing on edibles, particularly high-resolution drop-on-demand ink-jet printing, usually requires the use of low viscosity inks which are readily ejectable through the tiny orifices of the ink-jet printhead. Further, the inks themselves must be edible. The dyes and colorants approved for human consumption under the Food, Drug and Cosmetic Act (FD&C) administered by the U.S. Food and Drug Administration (FDA) are all water-soluble, as are all the FDA approved natural colorants, which essentially limits such applications to using water-based inks.
Generally, these edible, low viscosity inks useful in ink-jet processes for printing on edibles are of necessity water-based. As a consequence of being water-based, the known food-grade ink-jet inks have a relatively high polarity as compared to solvent-based inks.
A protective and decorative glaze is typically coated on the surface of many hard panned sugar shell confections. Often, these additional coatings are low polarity materials, such as carnauba wax. Printing with low viscosity inks on shaped, non-planar surfaces at high rates of production, particularly on those confectionery having such low polarity surfaces, presents significant challenges. The water-based inks tend to bead up on the surface and ate difficult to dry which leads to smearing
Thus, there continues to be a need in the industry for methods of ink-jet printing on edibles which have surface finishes that are difficult to print on.